Serine Enzyme Inhibitor Research Articles

Enzyme Inhibitors as Multifaceted Tools in Medicine and Agriculture.

Enzymes are molecules that play a crucial role in maintaining homeostasis and balance in all living organisms by catalyzing metabolic and cellular processes. If an enzyme's mechanism of action is inhibited, the progression of certain diseases can be slowed or halted, making enzymes a key therapeutic target. Therefore, identifying or developing enzyme inhibitors is essential for treating significant diseases and ensuring plant defense against pathogens. This review aims to compile information on various types of enzyme inhibitors, particularly those that are well studied and beneficial in both human and plant contexts, by analyzing their mechanisms of action and the resulting benefits. Specifically, this review focuses on three different types of enzyme inhibitors that are most studied, recognized, and cited, each with distinct areas of action and potential benefits. For instance, serine enzyme inhibitors in plants help defend against pathogens, while the other two classes-alpha-glucosidase inhibitors and carbonic anhydrase inhibitors-have significant effects on human health. Furthermore, this review is also intended to assist other researchers by providing valuable insights into the biological effects of specific natural or synthetic inhibitors. Based on the current understanding of these enzyme inhibitors, which are among the most extensively studied in the scientific community, future research could explore their use in additional applications or the development of synthetic inhibitors derived from natural ones. Such inhibitors could aid in defending against pathogenic organisms, preventing the onset of diseases in humans, or even slowing the growth of certain pathogenic microorganisms. Notably, carbonic anhydrase inhibitors have shown promising results in potentially replacing antibiotics, thereby addressing the growing issue of antibiotic resistance.

PANCREATIC ENZYMES GENERATE CYTOTOXIC MEDIATORS IN THE INTESTINE

Recent evidence indicates that shock is accompanied by a failure of the mucosal barrier in the intestine and entry of pancreatic digestive enzymes into the wall of the intestine. To investigate the formation of cytotoxic mediators produced by enzymatic digestion of the intestine, we applied homogenates of rat small intestinal wall to human neutrophils and used flow cytometry measurements of propidium iodide uptake to determine cytotoxicity. We show that homogenates of the small intestine after ischemia by occlusion of the superior mesenteric and celiac arteries for 3 h, but not without ischemia, are cytotoxic. Digestion of homogenates of nonischemic intestinal wall with purified trypsin, chymotrypsin, or elastase, proteases normally present in the intestinal lumen, yielded cytotoxic mediators. Before cell death, we saw cell damage in the form of bleb formation and flow cytometry measurements of cell size changes due to blebbing. Cytotoxicity was prevented by serine protease inhibition with phenylmethylsulfonyl fluoride (PMSF) before, but not after proteolytic digestion of the wall homogenates, indicating that enzymatic action of proteases on the homogenate is necessary for cytotoxicity. Cytotoxicity of wall homogenates digested by enzymes in the fluid collected from the lumen of the intestine was greater than digests by the individual purified proteases. Cytotoxicity is undetectable if digestive enzymes in the luminal fluid are inhibited with a combination of enzyme inhibitors PMSF and 6-amidino-2-naphthyl p-guanidinobenzoate dimethanesulfonate before addition of wall homogenates. Passage of digested intestinal wall homogenates across a hydrophobic glass-fiber filter reduced cytotoxicity. Furthermore, we found that luminal fluid itself may be cytotoxic, possibly because of digestion of ingested food. To test whether digested food can be cytotoxic, we homogenized rat food and digested it in vitro with chymotrypsin or endogenous enzymes in luminal fluid. Cytotoxicity was significantly increased after digestion of food by luminal fluid compared with luminal fluid or undigested food. These results indicate the presence of a previously unknown mechanism for hemorrhagic necrosis in shock.

β-Lactams as Inhibitors of Serine Enzymes: An Update

The developments in the area of inhibition of different serine enzymes by βlactams have been reviewed recently [1]. Since then, the following advances have been made: development of synthetic methodology for the preparation of enantiomerically pure lactams, whose inhibiting properties have been previously established; preparation of novel antibacterial cephams; synthesis of prodrugs containing dual inhibitors of PBPs and βlactamases; and the discovery of monocyclic βlactams, whose mode of action and structure-activity profiles differ dramatically from those of traditional βlactam drugs.

Isolation and properties of a tripeptidyl peptidase from a periodontal pathogen Prevotella nigrescens

Prolyltripeptidyl amino peptidase activity was found in a crude extract of Prevotella nigrescens and this enzyme was purified by procedures including concentration with ammonium sulfate, ion exchange chromatography, gel filtration, and isoelectric focusing. This peptidase hydrolyzed Ala-Ala-Pro- p-nitroanilide as well as Ala-Phe-Pro- p-nitroanilide. Furthermore, several p-nitroanilide derivatives of dipeptides with a proline residue in the second position from the amino-terminal end (Xaa-Pro) were also cleaved detectably. The molecular mass of this tripeptidase was calculated as 56 kDa and its isoelectric point was 5.8. The enzyme was inactivated completely by heating at 60°C for 5 min and inhibited significantly by specific serine enzyme inhibitors.

β-Lactams as Inhibitors of Serine Enzymes

For nearly six decades, penicillins have been used widely to treat bacterial infections. The development of multidrug resistance, however, has reduced the effectiveness of β-lactams as antimicrobial drugs. A main contributor to b-lactam resistance is the production of β-lactamases, and the development of β-lactamase inhibitors has been one of the main strategies in antimicrobial drug development. In recent years, microbial resistance to existing β-lactamase inhibitors has emerged, spurring investigations in the area of β-lactamase dependent prodrugs that incorporate a bactericidal moiety. In a similar fashion cytotoxic prodrugs have been developed as a means of anticancer therapy. Recently, certain β-lactams have been identified as inhibitors of serine enzymes produced by viruses, fungi and mammals. Development of β-lactam inhibitors of enzymes which have active-site serine, such as human leukocyte elastase, human cytomegalovirus protein, prostate specific antigen, thrombin, herpesvirus, co-enzyme A independent transacylase, γ-aminobutyric acid (GABA) aminotransferase, and human cytosolic phospholipase A2, has attracted interest in all areas of medicinal chemistry. Efforts have been directed toward identification of the structure-activity relationship of the newly developed or modified β-lactams, as well as enrichment of the arsenal of existing methods for asymmetric synthesis and application of novel analytical techniques, such as ESIMS for β-lactam-enzyme complex identification. The present review intends to draw attention to the versatility of the β-lactams as serine enzyme inhibitors. Keywords: lactam, bacterial resistance, serine enzyme, serine enzyme inhibitor

Purification and characterization of a unique alkaline elastase from Micrococcus luteus.

Micrococcus luteus isolated from human skin secretes an alkaline protease which degrades elastin. M. luteus protease (MLP) was produced in the late logarithmic and stationary phases of growth. MLP, purified to homogeneity by a three-step process, had a molecular mass of 32,812 Da and an isoelectric point of 9.3. MLP was active and highly stable in solution for 24 h from pH 6.0 to 10.5; it had maximal activity at temperatures between 57 and 59 degrees C. The presence of calcium in the solution was essential for enzyme activity and to prevent autolysis. Optimal activity occurred between pH 9.0 and 9.5, with 60% maximal activity from pH 6.5 to 11.0. The enzyme was inhibited by the serine enzyme inhibitors phenylmethylsulfonyl fluoride and chymostatin but not by the metalloenzyme inhibitor 1,10-phenanthroline or sulfhydryl enzyme inhibitors. Casein, bovine serum albumin, ovalbumin, beta-lactoglobulin, and elastin were digested by the protease while collagen and keratin were resistant to digestion. MLP demonstrated both esterase and amidase activity on synthetic peptide substrates. MLP preferentially cleaved the Leu(15)-Tyr(16) and Phe(24)-Phe(25) bonds of the oxidized beta-chain of insulin. Longer digests of insulin and the pattern of activity against synthetic substrates suggest that MLP has a cleavage specificity for bulky, hydrophobic, or aromatic amino acids in the P(1) or P(1)' positions. Amino acid sequences from the N-terminus and internal peptides of MLP were unique.

Purification and characterization of an extracellular proline iminopeptidase from Arthrobacter nicotianae 9458.

An extracellular proline iminopeptidase, with a molecular mass of about 53 kDa, was purified from Arthrobacter nicotianae 9458 and characterized. The enzyme had temperature and pH optima of 37 degrees C and 8.0, respectively, was completely inactivated by heating for 1 min at 80 degrees C and showed highest activity on Pro-pNA. The proline iminopeptidase was characterized by activity at low temperature, NaCl concentrations up to 7.5% and by high sensitivity to pH values 6.0, serine enzyme inhibitor PMSF and divalent cations, Fe2+, Sn2+, Cu2+, Zn2+, Hg2+, Co2+ and Ni2+. The extracellular proline iminopeptidase from A. nicotianae 9458 was able to hydrolyze proline-containing peptides at the pH, temperature and NaCl concentration typical of the surface of smear-ripened cheese and may contribute to proteolysis of these cheeses during ripening.

Purification and characterization of an extracellular proline iminopeptidase from Arthrobacter nicotianae 9458

An extracellular proline iminopeptidase, with a molecular mass of about 53 kDa, was purified from Arthrobacter nicotianae 9458 and characterized. The enzyme had temperature and pH optima of 37°C and 8.0, respectively, was completely inactivated by heating for 1 min at 80°C and showed highest activity on Pro-pNA. The proline iminopeptidase was characterized by activity at low temperature, NaCl concentrations up to 7,5% and by high sensitivity to pH values 6.0, serine enzyme inhibitor PMSF and divalent cations, Fe 2+, Sn 2+, Cu 2+, Zn 2+, Hg 2+, Co 2+ and Ni 2+. The extracellular proline iminopeptidase from A. nicotianae 9458 was able to hydrolyze proline-containing peptides at the pH, temperature and NaCl concentration typical of the surface of smear-ripened cheeses and may contribute to proteolysis of these cheeses during ripening.

Purification and properties of cephalosporin-C deacetylase from the yeast, Rhodotorula glutinis 38B1, useful for bioconversion of 7-aminocephalosporanic acid derivatives

A 7-aminocephalosporanic acid (7-ACA) deacetylating enzyme was purified to homogeneity from Rhodotorula glutinis 38B1, whose resting cells have been previously reported as useful for the conversion of 7-ACA derivatives [Sakai et al., Appl. Environ. Microbiol., 62, 2667–2672, 1996]. The purified enzyme was a dimer comprised of identical subunits with a molecular mass of 82 kDa. The purified enzyme used cephalosporin C and several 7-ACA derivatives with low K m and high k cat values as substrates, as well as some acetyl esters with relatively long-chain alcohols. Based on this substrate specificity, the enzyme is classified as cephalosporin-C deacetylase (EC 3.1.1.41). The enzyme was most active at 35°C and pH 5.5, and was inhibited by several serine enzyme inhibitors. The purified enzyme was glycosylated on the addition of an asparagine-linked “hybrid type” oligosaccharide, and most of the enzyme activity was found in the purified cell wall fraction. The enzyme localization and kinetic properties explain the high efficiency of 7-ACA deacetylation in a resting-cell reaction.

Lipase activity and gene cloning of Acinetobacter calcoaceticus LP009.

The production of lipase from Acinetobacter calcoaceticus LP009, a bacterium isolated from raw milk, was found to be best induced by Tween-80 at 1.0% concentration. It was efficiently secreted, and only a minute amount of activity was detected at the cell surface and intracellularly. A. calcoaceticus LP009 lipase exhibited maximum activity at pH 7.0 and 50 degrees C, and was relatively stable upon storage at pH 5.0 to 7.0 and at 4, 30, or 37 degrees C. The enzyme was found to be inactivated by EDTA suggesting that it was a metalloenzyme. Its activity was reduced by less than 20% with the addition of various ions to reaction mixtures, but long storage with them caused approximately 50% reduction in subsequent reactions under standard conditions. By contrast, the addition of Fe(3+) enhanced activity. The enzyme was highly stable upon storage with 0.1% of Triton X-100, Tween-80 or Tween-20, but highly unstable with various organic solvents tested. PMSF, a serine enzyme inhibitor, and 2-mercaptoethanol, a reducing agent, did not affect enzyme activity. After extraction and transfer, the lipase gene was efficiently expressed in recombinant Aeromonas sobria. This recombinant strain was shown to have increased hydrolyzing efficiency and have high potential for lipid-rich wastewater treatment.

The gene for albicidin detoxification from Pantoea dispersa encodes an esterase and attenuates pathogenicity of Xanthomonas albilineans to sugarcane.

Albicidin phytotoxins are pathogenicity factors in a devastating disease of sugarcane known as leaf scald, caused by Xanthomonas albilineans. A gene (albD) from Pantoea dispersa has been cloned and sequenced and been shown to code for a peptide of 235 amino acids that detoxifies albicidin. The gene shows no significant homology at the DNA or protein level to any known sequence, but the gene product contains a GxSxG motif that is conserved in serine hydrolases. The AlbD protein, purified to homogeneity by means of a glutathione S-transferase gene fusion system, showed strong esterase activity on p-nitrophenyl butyrate and released hydrophilic products during detoxification of albicidins. AlbD hydrolysis of p-nitrophenyl butyrate and detoxification of albicidins required no complex cofactors. Both processes were strongly inhibited by phenylmethylsulfonyl fluoride, a serine enzyme inhibitor. These data strongly suggest that AlbD is an albicidin hydrolase. The enzyme detoxifies albicidins efficiently over a pH range from 5.8 to 8.0, with a broad temperature optimum from 15 to 35 degrees C. Expression of albD in transformed X. albilineans strains abolished the capacity to release albicidin toxins and to incite disease symptoms in sugarcane. The gene is a promising candidate for transfer into sugarcane to confer a form of disease resistance.

Purification and characterization of lipase from Aeromonas sobria LP004

Lipase from Aeromonas sobria LP004, isolated from raw milk, was purified and characterized. The lipase was purified 10.29 fold to a homogeneous state by ultrafiltration and column chromatography on phenyl sepharose. The molecular weight of the lipase determined by SDS-PAGE was 97 kDa. Purified A. sobria LP004 lipase exhibited the maximum activity at pH 6.0 and 45°C and was stable under alkaline conditions (pH 6.5–10.0) and at temperatures lower than 40°C. This lipase could be classified as a 1,3-position specific enzyme and its catalytic activity was calcium dependent. PMSF, a serine enzyme inhibitor and 2-mercaptoethanol, a reducing agent, did not affect the enzyme activity.

Hydrolytic profile for ester- or amide-linkage by carboxylesterases pI 5.3 and 4.5 from human liver.

Carboxylesterases (EC 3.1.1.1) from human liver were purified using Q-Sepharose, Sephadex G-150, isoelectrofocusing and Con A-Sepharose. The calculated molecular mass of the pI 5.3 enzyme was 120 kDa and 61 kDa from the results of Sephadex G-150 gel filtration and SDS-polyacrylamide gel electrophoresis (PAGE), respectively, suggesting that this enzyme is a dimer. On the other hand, carboxylesterase pI 4.5, with a molecular mass of 64 kDa, was a monomer. The activities of both enzymes were inhibited by typical serine enzyme inhibitors. Amino acid sequence analysis of the purified enzymes pI 5.3 and 4.5 showed high homology with rabbit carboxylesterase form 1 and 2, respectively. The results also suggested that carboxylesterase pI 5.3 is identical to the deduced amino acid sequence from cDNA for HU1, and that carboxylesterase pI 4.5 is identical to the deduced amino acid sequence from the cDNA registered as human carboxylesterase (hCE-2) in GenBank. We first purified carboxylesterase pI 4.5 and investigated its hydrolytic activity upon various drugs. The two enzymes differed in substrate specificity. Prodrugs of angiotensin-converting enzyme inhibitors, such as delapril and imidapril, were converted to active metabolites by carboxylesterase pI 5.3, but not by carboxylesterase pI 4.5. The hydrolysis velocity of temocapril by carboxylesterase pI 5.3 was 12-fold faster than by carboxylesterase pI 4.5. In contrast, aspirin, oxybutynin and procaine were hydrolyzed by only carboxylesterase pI 4.5. We also found that an amide-linkage in drugs, except for that in aniracetam, was not a good substrate for the two enzymes. Consequently, carboxylesterases pI 5.3 and 4.5 may be involved in the metabolism of various drugs containing an ester-linkage.

Alkynyl phosphates are potent inhibitors of serine enzyme

Propynyl, hexynyl and t-butylethynyl diethyl phosphates were found to be very powerful covalent inhibitors of serine enzymes. Esterases were inhibited with second-order rate constants of 10 7–10 8 M −1 min −1. Most proteases were inhibited with a rate constant of 10 4–10 5 M −1 min −1. By inhibiting chymotrypsin with (3- 14C)-1-propynyl diethyl phosphate, it was established that inhibition was caused by binding of the phosphate group to the enzyme active site.

Purification and characterization of a new aminopeptidase from Lactobacillus delbrueckii subsp. bulgaricus B14

Abstract An aminopeptidase was purified from crude extracts of Lactobacillus delbrueckii subsp. bulgaricus B14 by ammonium sulphate precipitation, anion exchange chromatography over DEAE-Sepharose, hydroxy apatite chromatography, and FPLC anion exchange chromatography on Mono Q . By HPLC gel filtration, a molecular mass of ∼260 kDa was estimated. SDS polyacrylamide gel electrophoresis resulted in a single protein band with a molecular mass of ∼32 kDa. Optimal aminopeptidase activity was obtained at pH 6·5 and 45°C. The enzyme was activated by Mg 2+ , Co 2+ and Zn 2+ at concentrations up to 0·1 mM. Higher concentrations of these metal ions inhibited peptidase activity. Ca 2+ increased enzyme activity even at concentrations of 10 mM. Metal chelating agents inhibited enzyme activity strongly whereas thiol group- and serine enzyme inhibitors as well as reducing agents had no remarkable effect on peptidase activity. The EDTA-inhibited enzyme could be reactivated by the divalent cations Co 2+ and Zn 2+ . Best substrates among the hydrolyzed di- and tripeptides were Leu-Leu-Leu, Leu-Gly-Gly, Leu-Ala-Pro and Leu-Leu. Amino acid- and peptide- nitroanilides were cleaved at a lower rate. For the substrates Leu-Leu-Leu, Leu-Gly-Gly, and Leu-Leu, K m -values of 0·14, 1·37 and 1·52 mM were calculated, respectively.

Fractionation of Elastase-Type Enzyme Activity in Biological Fluids Using a Centrifugal Analyser

We here describe a simple, rapid and sensitive spectrophotometric method for fractionation of elastase-type enzyme activity on a centrifugal analyser using the chromogenic substrate Suc-[Ala]3-pNA. For quantitation of metalloelastase and serine elastase, respectively, the method utilizes 20mM EDTA as ametalloenzyme inhibitor and the serine enzyme inhibitor soybean trypsin inhibitor (SBTI) in a final concentration of 2.5 g/l. Containing both serine- and metalloelastase, a pool of synovial fluids from patients with rheumatoid arthritis was used. The method is suitable for clinical studies on different body fluids or cell constituents. The investigation points out the necessity of using inhibitors when chromogenic substrates are used to measure elastase activity in biological fluids.

Expression in Xenopus oocytes of rat liver mRNA coding for a bile salt-dependent cholesteryl ester hydrolase.

A catalytically active bile salt-dependent cholesteryl ester hydrolase (CEH) was expressed when Xenopus oocytes were injected with rat liver mRNA. The expressed CEH activity was highly dependent on the presence of trihydroxy bile salts (cholate or one of its conjugates); maximum hydrolytic activity was observed in the presence of 10 mM sodium cholate. The expressed CEH was not activated by dihydroxy bile salts (deoxycholate and its conjugates). In the presence of 10 mM sodium cholate, the CEH activity was maximal near pH 7 but was significant between pH 6 and 8. Monospecific immune IgG raised against rat pancreatic CEH completely inhibited the CEH expressed in Xenopus oocytes. Phenylmethylsulfonyl fluoride, a serine enzyme inhibitor, was inhibitory to the expressed CEH activity, whereas p-chloromercuribenzoate (up to 5 mM), a potent thiol-blocking agent, did not significantly inhibit the expressed activity. These experiments clearly demonstrate that the liver contains an mRNA encoding a bile salt-dependent CEH activity and suggest that the uptake of pancreatic enzyme is not necessarily the source of liver CEH as has been speculated.

The interaction of alkynyl carboxylates with serine enzymes a potent new class of serine enzyme inhibitors

The recently reported alkynyl esters, propynyl benzoate and propynyl p-methoxybenzoate, were found to interact with a variety of serine enzymes. α-Chymotrypsin was inhibited very rapidly by an equivalent amount of the esters. Trypsin, elastase and pronase were also inhibited by the esters. On the other hand, liver esterase started to hydrolyse the alkynyl esters rapidly, but the enzyme became inhibited during the course of reaction. The inhibited enzymes exhibited slow reactivation which could be considerably enhanced by hydroxylamine.

Histochemical demonstration of chymotrypsin like serine esterases in mucosal mast cells in four species including man.

Serine esterases were detected in the granules of mucosal mast cells from rat, mouse, sheep, and man. Successful demonstration of enzyme activity required brief fixation (6 h) of tissues in 4% paraformaldehyde. Staining with naphthol AS-D chloroacetate produced an intense red reaction product in intraepithelial mucosal mast cells (globule leucocytes) and mucosal mast cells within the lamina propria of the gastrointestinal tract. The mast cell identity of cells stained for esterase was confirmed by sequential staining with toluidine blue (pH 0.5). Furthermore, the numbers of cells detected after staining for esterases or with toluidine blue were highly correlated. Esterase activity within mucosal mast cells/globule leucocytes from all species was inhibited with the serine enzyme inhibitor phenylmethylsulphonyl fluoride. Further histochemical studies with the substrate, N-acetyl-DL-phenylalanine B-naphthyl ester, indicated that mucosal mast cells and globule leucocytes contain esterases which are chymotrypsin like in substrate specificity.

An N-acetylmuramidase induced by PL-1 phage infection of Lactobacillus casei.

A lytic enzyme was isolated and purified from PL-1 phage-induced lysates of the host Lactobacillus casei ATCC 27092. The molecular weight of the enzyme was about 30000. Maximum activity on the lysis of the host cell walls occurred at pH 6.0-6.5 and at 45 degrees C. The enzyme activity was inhibited by heavy metal ions, SH- and serine-enzyme inhibitors and o-phenanthroline. The reducing end of the enzymic digest was muramic acid and the enzyme was considered to be an endo-N-acetylmuramidase. However, the enzyme differed from the other known N-acetylmuramidases including hen's egg-white lysozyme in several enzymic properties.